. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Casting innOVatiOns
molding, coresetting, pouring and grind- ing, so its process is more repeatable, accurate and quick, according to Jed Falgren, the company’s vice president. For example, automatic coresetting al- lows Dotson to reduce the amount of fl ash produced on the track pad castings, making it possible to remove it more rap- idly with automatic grinders. Dotson also designed and built a new punch press to trim all eight square holes in the casting at the same time. This further reduced the process time required. For the connecting linkage, Dotson
utilized defect mapping to eliminate soft core areas that previously led to surface imperfections. By casting fea- tures to tight tolerances and accurately setting cores with an automatic core setter, the grinding step was eliminated. “Dotson provided a quality part
at a reasonable price in a reasonable amount of time,” Nistler said. According to Falgren, Dotson also
was able to provide Grouser its cast track pads and connecting linkage according to demand, reducing large inventories on hand.
“They can order what they want and
have the right inventory to meet their customers’ demands. Our short leadtime, coupled with superior on-time perfor- mance gives our customers the ability to react quickly and confi dently to market fl uctuations.,” Falgren said.
METAL
from manual green sand molding to fully automated molding, many of the casting jobs required design changes. Impellers represent a particu-
J
lar challenge because of the wide variation between the heavy and thin sections. The metalcaster was experiencing problems in the early transition from manual to automatic molding patterns, and the process was becoming costly. “This part was becoming a serious
problem,” said Dan Rudolph, quality engineer for J. Walter Miller. “We had spent about eight weeks and $5,000
Simulation Aids in Impeller Redesign
Walter Miller Co., Lancaster, Pa., produces brass and bronze castings for the fi re protection, pumping and valve industries. When the company converted
trying to fi x the problem and did not seem to be making progress.” The metalcasting facility turned to
the QuikCast software from ESI Group, Bloomfi eld Hills, Mich., to perform solidifi cation modeling. One particular impeller was pro-
duced in a squeezer mold using an open riser fed by a large overhead mass of molten metal. This con- fi guration was not possible with the automatic molding machine, which uses fi xed riser or sprue locations with a maximum contact diameter of 1 in. The open riser was replaced by a 1-in. sprue, reducing the contact area. When the new confi guration was tried on the automatic machine, the impeller castings exhibited voids in the hub caused by the contraction
January/February 2010
Metal Casting Design & PurChasing
49
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